Southern watergrass is a perennial grass that forms dense colonies in shallow water. It's leaves can be underwater (to 3 feet), floating, or in dense colonies that can rise to 12 inches in height on stems to 3 feet long. Leaves are long and narrow (to 2 inches long).
Southern watergrass can be cut and the roots can be dug up but physical control is difficult because it can reestablish from seeds and remaining roots.
The active ingredients that have been successful in treating white water lily include glyphosate (G), fluridone (G). E = excellent, G = good
Avocet PLX is a liquid glyphosate formulation that has been effective on Emergent Plant. It is a broad spectrum, systemic herbicide. Systemic herbicides are absorbed and move within the plant to the site of action. Systemic herbicides tend to act more slowly than contact herbicides. An aquatically registered surfactant (see the label) will have to be added to the glyphosate solution for good results.
WhiteCap is a fluridone compounds that has been effective on white water lily. These are broad spectrum, systemic herbicides. Systemic herbicides are absorbed and move within the plant to the site of action. Systemic herbicides tend to act more slowly than contact herbicides.
GullWing contains the active ingredient, imazapyr, which inhibits the plant enzyme AHAS (acetohydroxyaced synthase). GullWing is a systemic herbicide that is effective on post-emergent floating and emergent aquatic vegetation. Imazapyr is effective at low-volume rates and does not contain heavy metals, organochlorides or phosphates, making it safe to humans and livestock. GullWing requires the use of a spray adjuvant when applying on post-emergent vegetation.
Information and photos courtesy of:
Department of Wildlife and Fisheries Sciences, Texas A&M University